Mediterranean invasive species factsheet www.iucn-medmis.org

Species report Limnoperna (Xenostrobus) securis

(Black pygmy ) AFFILIATION MOLLUSCS

SCIENTIFIC NAME AND COMMON NAME REPORTS Limnoperna (Xenostrobus) securis 2

Key Identifying Features

The thin, elongated shell, almost triangular in shape, is formed of two valves of similar shape and size. The shell is shiny and smooth, with a sculpture of fine concentric lines. Young individuals are yellowish brown, while the adults are dark brown or black, up to 2–3 cm in length. The interior of the shell is iridescent blue.

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Other species that look similar

Identification and Habitat

The black pygmy mussel is found exclusively in estuaries and lagoons, often together with the mussel Mytilus galloprovincialis, on any kind of submerged or partially emergent hard substratum or oyster shells and occasionally also on sandy and muddy bottoms in crevices and holes. It is a filter-feeder of microscopic plankton and organic particles. These small form dense clumps of up to 50,000 individuals per square metre attaching themselves to the substrate with strong threads.

Adults can survive several days out of the water; they are tolerant of wide ranges of salinity, oxygen concentration and temperature. The History and Route of species is not found in the sea or in the Introduction downstream parts of estuaries where salinity is Originally from the south-eastern Pacific (New constantly high. Zealand and southern Australia), L. securis was first reported in the Mediterranean in Italy (in Reproduction the Po river delta) in 1992. Since then, it has been found in coastal lagoons and estuaries of The facility with which the pygmy mussel France and Italy (the Tyrrhenian, Ligurian and reproduces partially explains its success as an Adriatic Seas) and Spain (northern Catalonia). It invader. It is a fast-growing species with a short was accidentally introduced with seed bivalves life span, living on average for only 1 year or for aquaculture purposes, but it can also be occasionally 2–3 years. Fertilization takes place spread in ships’ ballast waters (water pumped in the water column and free swimming larvae into and out of ships to adjust their buoyancy) or disperse on water currents, helping to colonize by fouling (in the communities encrusting a new habitats. ship’s hull).

Similar Species

Limnoperna securis resembles the common Mediterranean species, minimus. The major differences are that L. securis: 1) has a generally darker shell; 2) is narrower and more elongated, whereas M. minimus is squatter in shape; 3) lacks internal shell teeth where the two valves are hinged; 4) is adapted to living at low salinities, unlike M. minimus which is found in marine waters.

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Ecological Impacts Barbierie et al., 2011. New records of the pygmy mussel Xenostrobus securis (: ) Considered to be one of the worst invasive alien in brackish-water biotopes of the western species in Europe (European Environment Mediterranean provide evidence of its invasive Agency, 2007), its gregarious behaviour and potential. Marine Biodiversity Records, Vol 4, 1-4 high-density populations living on muddy bottoms can smother the native infaunal communities. Due to its high filtration rates, it may affect nutrient cycling, reducing the food available to other filter-feeders; it is therefore a major competitor of native species. It can also produce changes in the physico-chemical characteristics of the habitat and affect turbidity and sedimentation.

Economic Impacts

The species’ economic impact has not yet been quantified, but it is highly possible that bivalve culture and harvesting may suffer due to strong competition. By overgrowing commercially harvested molluscs, especially the mussel Mytilus galloprovincialis, it can reduce their growth and yield. L. securis can act as a key host for pathogens of commercially cultured species. Its rapid growth can contribute to the fouling of submerged structures, pipelines, ropes and boat hulls.

Management Options

Suggested prevention measures include conducting local public awareness campaigns combined with the monitoring of populations, which makes early detection possible. Black pygmy mussels should be removed from seed bivalves intended for mariculture purposes. Control: eradication of this species from the environment is unfeasible at the moment due to its small size and the large numbers of individuals forming new populations.

Further Reading http://www.ciesm.org/atlas/Xenostrobussecuris.html

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Legend

Algae Angiosperm Cnidarians Centre for Mediterranean Molluscs Crustaceans Ascidians Cooperation Combjellies / Fishes Ctenophores

More Information: Guide and reports platform for Marine Protected Areas (MPAs) in the Mediterranean. www.iucn-medmis.org

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MPAs, Country Date Density Measure

Secche della Meloria, Italy Before 2013 -- --

Aiguamolls de l'Alt Emporda, Spain Before 2013 -- --

How to cite this tab: Limnoperna (Xenostrobus) securis - Invasive Alien Species Fact Sheet for Mediterranean Network of MPAs. From Online Database MedMIS (IUCN Center for Mediterranean Cooperation, Download date 01/10/2021.

More information about this species from: Otero, M., Cebrian, E., Francour, P., Galil, B., Savini, D. 2013. Monitoring Marine Invasive Species in Mediterranean Marine Protected Areas (MPAs): A strategy and practical guide for managers. Malaga, Spain: IUCN. 136 pages www.iucn.org/dbtw-wpd/edocs/2013-008-Es.pdf .

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